GOP Candidates Shift Focus To National Security As First Voting NearsThe calendar has finally turned to 2016, and the Republican presidential candidates are ramping up their campaigning. The theme this week is national security, an issue that unites the GOP establishment and the conservative grassroots.

The calendar has finally turned to 2016, and the Republican presidential candidates are ramping up their campaigning. The theme this week is national security, an issue that unites the GOP establishment and the conservative grassroots.

KELLY MCEVERS, HOST:

This is a big week for Republican presidential candidates. The holidays are over, and there is now less than a month to go before the first round of voting in the election, the Iowa caucuses. And the Republican theme of how scary the world has become under President Obama's watch is only getting more intense. With us now to talk about this is NPR national political correspondent Mara Liasson. And Mara, it really seems like almost all the Republican candidates are talking about the same thing right now. What's going on?

MARA LIASSON, BYLINE: Well, the theme is pretty clear. The world is on fire, and it's all President Obama's and Hillary Clinton's fault. Now national security and the fight against terrorism is an issue that almost always gives Republicans an advantage, and the president's numbers on this are very bad right now. People don't feel he's kept them safe. And not only is this an issue that's worked for the Republicans in the past, but it has the added value of uniting the Establishment and Grassroots Conservative wings of the GOP. And here's a sample of what we heard from Republicans just today. First, an ad from Jeb Bush airing in New Hampshire.

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JEB BUSH: We are at war with radical Islamic terrorism. We have but one choice, to defeat it.

LIASSON: Here's Chris Christie giving a national security speech in New Hampshire today.

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CHRIS CHRISTIE: These are among the most dangerous and perilous times in our country's recent history. These times and these challenges demand a grown-up to be our candidate.

LIASSON: And Marco Rubio also giving a national security speech in New Hampshire.

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MARCO RUBIO: When America needed a bold plan of action from our commander-in-chief, we instead got a lecture on love and tolerance and gun control. It was designed to please the talking heads at MSNBC. The result of all this is that people are afraid, and they have every right to be.

LIASSON: So this is a theme that's been building for months in the GOP race. But as you can hear, this is a very, very dark picture they're painting of the state of the world. Voters are afraid and, says Marco Rubio, they should be afraid. This makes perfect political sense for an opposition party which is anticipating running against a de facto incumbent, Hillary Clinton, the former secretary of state of the current administration.

MCEVERS: With all this ominous language that we're hearing, there is one voice that I haven't heard yet and that's Donald Trump.

LIASSON: We did hear from him today. Donald Trump aired his first TV ad. He has rocketed to the top of the polls and stayed there without spending hardly any money on advertising, but now he says he's going to spend a couple million dollars a week to air this.

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UNIDENTIFIED MAN: He'll quickly cut the head off ISIS and take their oil, and he'll stop illegal immigration by building a wall in our southern border that Mexico will pay for.

LIASSON: There's a little glitch in that ad when you hear that line about the border and the wall. You see footage of what turns out to be refugees in Morocco running to a border. But the point is Trump is doubling down here. There's nothing new in the ad. It's a kind of Donald Trump's greatest hits. But he is using a narrator, an outside voice, which is run-of-the-mill for most candidates, but Trump hasn't seemed to need anyone to vouch for him but himself. But here, the narrator's voice serves as a powerful outside validator. It makes Trump seem more like a typical candidate, something most politicians wouldn't want. But in Trump's case, it probably helps.

MCEVERS: And quickly, what is the state of play in the Republican primary? As you said, Trump is still on top, right?

LIASSON: Trump is still on top in most state polls, but not Iowa, where Cruz is ahead. But inside all those anti-Obama national security speeches today is a furious intramural battle. You heard both Christie and Rubio disparage a candidate who they said was running to be entertainer-in-chief. Translation? Donald Trump. Rubio said you can't defeat ISIS with a filibuster, that's a clear swipe at Ted Cruz. So here we are, 27 days from the first votes, and the race is still very, very unsettled on the Republican side.

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